As a method of polishing a workpiece, there is widely used blasting processing of injecting abrasive grains along with compressed air as a gas-solid two-phase flow from a nozzle toward the workpiece, causing the abrasive grains to collide with or contact with the workpiece, and thereby, polishing the workpiece. A generally used blasting processing device includes a recovery part formed into a funnel shape. The recovery part is provided in a lower part of a blasting chamber for performing the blasting processing on the workpiece. This blasting processing device sucks and recovers powder dust (injected blasting abrasives and cutting powder of the workpiece) having fallen in the recovery part, sorts it into reusable blasting abrasives and other fine particles (abrasive grain in which cracks or defects arise and the cutting powder of the workpiece) with a classification device, and after that, performs the blasting processing again with the reusable blasting abrasives (for example, Patent Literature 1). In such a blasting processing device, since the abrasive grains scatter in the whole large-capacity blasting processing chamber, it is difficult to completely prevent powder dust from scattering outside the blasting processing chamber in exchanging workpieces or the similar situation. Moreover, since high suction performance is required for equipment that generates suction force, there is a problem that the whole blasting processing device increases in size.
To efficiently recover the powder dust, there is disclosed a blasting processing device having a configuration of including a cover joined to suction equipment in the vicinity of the nozzle outlet, preventing powder dust from scattering with the cover, and recovering powder dust staying in the cover with the suction equipment (for example, Patent Literature 2). Since such a blasting processing device can be applied only when the processed surface is a sufficiently large flat surface with respect to the nozzle, the blasting processing device that has this configuration cannot be used depending on the shape of the workpiece.
In blasting processing, the injection pressure of a gas-solid two-phase flow is typically 0.2 MPa or more to be high. Therefore, there are a problem that the workpiece itself is blown off with the gas-solid two-phase flow and a problem that the abrasive grains stick into the workpiece, depending on the shape or the dimension of the workpiece.